Porous Medium Sensor

ABSTRACT

A porous medium sensor comprises: a sensing portion, a gas exchange tubing, a gas permeable protection sleeve, and a water impermeable distal end collar. The sensing portion is at least partially insertable in a porous medium and has a housing with a gas exchange aperture defined therein and a parameter sensor mounted in the housing for measuring a parameter of the porous medium in which the sensing portion is insertable. The gas exchange tubing is in gas communication with the gas exchange aperture of the sensor portion and has a water-repellent membrane inserted therein. The water-repellent membrane prevents water infiltration in the housing through the gas exchange aperture. The gas permeable protection sleeve covers at least a section of the gas exchange tubing. The water impermeable distal end collar covers a distal end of the gas permeable protective sleeve and the water-repellent membrane.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to porous medium sensors for measuring parametersor properties in porous media and, more particularly, it relates to aporous medium sensor having a sensing portion insertable in the porousmedium with a reference port in gas communication with ambient air.

2. Description of the Prior Art

Porous medium sensors for monitoring parameters in soil are known. Forexample, tensiometers monitor matrix water potential ψ_(m) (or soilmoisture tension), which is an indirect measure of soil water content.Tensiometers are used in irrigation scheduling to help farmers and otherirrigation managers to determine when to water. Tensiometers can also beused in the scientific study of soil and plant behaviors.

Typically the porous medium sensors are partially inserted in growingmedia, such as soil, for monitoring purposes. They include a sensingportion which is insertable in the growing medium and a head whichextends outwardly. A section of the housing can also extend outwardly ofthe growing medium.

Several porous medium sensors, such as tensiometers, have a referenceport in gas communication with ambient air. The reference port can beeither immersed in the growing medium or located outwardly of thegrowing medium when a sensing portion of the porous medium sensor isinserted therein. Water and porous medium infiltration into thereference port, can bias measurements taken in the growing medium, evenif the latter is located above the growing medium. To prevent thisproblem, it is known to cover the reference port with a water-repellentmembrane [See for instance US patent application no. 2010/0263436 filedon Apr. 30, 2010].

However, the water-repellent membrane can seal in heavy growing media,for instance the ones having high clay content. Furthermore, if thewater-repellent membrane is inserted in a fine growing media, a trappedvolume of air can surround the water-repellent membrane and also biasthe soil property measurements. Furthermore, water-repellent membranesdo not perfectly repel water in all conditions, particularly if the soilbecomes hydrophobic. In particular conditions, water and/or smallparticles can thus infiltrate the sensor through the reference port.

BRIEF SUMMARY OF THE INVENTION

It is therefore an aim of the present invention to address the abovementioned issues.

According to an aspect, there is provided a porous medium sensorcomprising: a sensing portion at least partially insertable in a porousmedium and having a housing with a gas exchange aperture defined thereinand a parameter sensor mounted in the housing for measuring a parameterof the porous medium in which the sensing portion is insertable; a gasexchange tubing in gas communication with the gas exchange aperture ofthe sensor portion and having a water-repellent membrane insertedtherein, the water-repellent membrane preventing water infiltration inthe housing through the gas exchange aperture; a gas permeableprotection sleeve covering at least a section of the gas exchangetubing; and a water impermeable distal end collar covering a distal endof the gas permeable protective sleeve and the water-repellent membrane.

According to another aspect, there is provided a porous medium sensorcomprising: a sensing portion at least partially insertable in a porousmedium and having a housing with a gas exchange aperture defined thereinand a parameter sensor mounted in the housing for measuring a parameterof the porous medium in which the sensing portion is insertable; a gasexchange tubing having a gas and water impermeable wall defining a gasexchange channel in gas communication with the gas exchange aperture ofthe sensing portion and a water-repellent membrane inserted in the gasexchange channel, the water-repellent membrane preventing waterinfiltration in the gas exchange channel through a distal open end ofthe gas exchange tubing; a gas permeable sleeve covering at leastpartially the gas exchange tubing and allowing gas communication withthe water-repellent membrane; and a water impermeable distal end collarcovering at least a section of the gas permeable sleeve and a section ofthe gas exchange tubing including the water-repellent membrane toprevent water infiltration therein.

In this specification, the term “porous medium” is intended to mean thesoil of a field in agriculture, or the soil of pots for growing plantsin a greenhouse or in a nursery, and any porous medium which fills withliquid. It can also be called a substrate, a mixture, a medium, or asoilless medium.

In this specification, the term “water-repellent” is defined as having adegree of resistance to permeability by and to damage caused by water inliquid form and therefore encompasses the common terms of “waterproof”and “hydrophobic”.

The present document refers to a number of documents, the contents ofwhich are hereby incorporated by reference in their entirety.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of the porous medium sensor in accordancewith an implementation;

FIG. 2 is a perspective view, enlarged and fragmented, of a distalsection of the porous medium sensor shown in FIG. 1;

FIG. 3 is a cross-section view of the distal section of the porousmedium sensor shown in FIG. 2;

FIG. 4 is a perspective view, enlarged and fragmented, of a proximalsection of the porous medium sensor shown in FIG. 1; and

FIG. 5 is a cross-section view of the distal section of the porousmedium sensor shown in FIG. 4.

It will be noted that throughout the appended drawings, like featuresare identified by like reference numerals.

DETAILED DESCRIPTION

Referring to the drawings and, more particularly, to FIG. 1, there isshown a porous medium sensor 120 and, more particularly, a tensiometerapparatus (or water potential sensor) in accordance with an embodiment.The tensiometer is designed to monitor matrix water potential in aporous medium such as, for instance, earthen soil or greenhouse soil.

The porous medium sensor 120 has a sensing portion 121 with a housing124 and a porous material tip 122. The porous material tip 122 extendsoutwardly from the housing 124 and is in direct contact with the porousmedium when inserted therein. The housing 124 encloses a parametersensor 123 (schematically represented in FIG. 1) for measuring aparameter of the porous medium in which the sensing portion 121 isinserted. The sensing portion 121 is designed to be at least partiallyinserted in the porous medium. In some implementations, the sensingportion 121, such as the one shown in FIG. 1, is designed to be whollyinserted in the porous medium. The design, the shape, and the componentsof the porous medium sensor 120 can vary from the above-described andillustrated embodiment.

The housing 124 has a gas exchange aperture 125 (FIG. 4) extendingthroughout an upper wall 128 thereof. In some implementations, the gasexchange aperture can extend throughout any wall of the housing 124,such as and without being limitative, the lateral wall 130 of thehousing 124. When the sensing portion 121 is partially or totallyinserted in the porous medium, the gas exchange aperture can also belocated in the porous medium. In the implementation shown in FIG. 1, thesensing portion 121 is totally insertable in the porous medium with thegas exchange aperture located in the porous medium.

The gas exchange aperture is a reference port of the porous mediumsensor 120. The gas exchange aperture is conceived to allow gas exchangebetween air located outside the housing, i.e. ambient air, and aninternal component (not shown) of the housing 124. For the tensiometershown in FIGS. 1 to 5, the gas exchange aperture is in gas communicationwith a pressure sensor (not shown) mounted in the housing 124. Thepressure sensor compares the liquid pressure in a fluid chamber to theatmospheric pressure, which is provided through the gas exchangeaperture, which is in gas communication with atmospheric gas.

Referring now to FIGS. 3 and 5, there is shown that, to prevent liquidsuch as water and porous medium infiltration in the gas inlet apertureand pressure variation due to porous medium surrounding the gas exchangeaperture, the gas exchange aperture is connected to a gas exchangetubing 132. The gas exchange tubing 132 is a tubular member with aperipheral wall 134 that defines a gas exchange channel 136. A proximalend 138 of the gas exchange tubing 132 is sealed to the housing 124 withthe gas exchange channel 136 being aligned with the gas exchangeaperture and in gas communication therewith. The gas exchange tubing 132is a flexible and elongated tubing made of a gas and liquid (water)impermeable material. Therefore, gas exchange with the gas exchangeaperture occurs through the internal gas exchange channel 136. In someimplementations (without limitation), the gas exchange tubing 132 ismade of nylon, Tygon®, water impermeable plastics, rubber or any otherwater impermeable tubing.

Referring now to FIGS. 2 and 3, there is shown that the gas exchangetubing 132 has a distal end 140, opposed to the proximal end 138 shownin FIGS. 4 and 5. To prevent water, growing medium particle or insectinfiltration in the gas exchange channel 136, which could flow in thehousing 124 through the gas exchange aperture, a water-repellentmembrane 142 is inserted in the gas exchange channel 136, close to thedistal end 140. In an embodiment, the water-repellent membrane 142 isinserted in the gas exchange channel 136 in less than about 1 inch fromthe distal end 140 of the gas exchange tubing 132. Gas exchange betweenatmosphere and the housing 124 occurs through the water-repellentmembrane 142, the gas exchange channel 136, and the gas exchangeaperture.

The water-repellent membrane 142 is porous and gas permeable, i.e. itallows gas communication between atmosphere and the housing 124. Thepressure on both sides of the water-repellent membrane 142 issubstantially equal. The response time of the water-repellent membrane142 to reach equilibrium is substantially fast. In an embodiment, thewater-repellent membrane 142 can substantially resist microbiologic andchemical degradation. The membrane shape, thickness, and size can varyin accordance with the porous medium sensor design.

The water-repellent membrane 142 is shaped to fill the gas exchangechannel 136 defined in the gas exchange tubing 132 and is tightlyinserted therein. If an adhesive is used to secure the water-repellentmembrane 142 to the gas exchange tubing 132, care should be taken toprevent or minimize membrane pore obstruction with the adhesive.

For instance, without being limitative, Teflon®, hydrophobicpolypropylene and polyethylene porous sheets, manufactured withfree-sintered materials, such as resins, glass, or metal beads can beused. These porous sheets provide filter media for ultrafine particlesand flowability of gases. The filtration obtained varies depending onthe micron size material selected.

The porous medium sensor 120 further includes one or a plurality ofelectric wires 175 (FIG. 3) having a proximal end operatively connectedto internal component(s) of the housing 124 and extending outwardlytherefrom. The electric wire(s) have an opposed distal end which can beconnected to a head (not shown) of the porous medium sensor 120 throughan electric connector 160 operatively connected to the electric wiredistal end. The head can include an electric circuit board (not shown)of the porous medium sensor 120. The electric wire(s) transfers dataacquired or monitored by the sensor 120 to the electronic circuit boardfor further processing. The electric wire(s) can also provide a powersupply to the sensor 120 and an electric/electronic circuit operativelyconnected to the sensor 120. The head can extend above the porous mediumwhen the sensing portion 120 is at least partially inserted therein.

In the embodiment shown, the electric wire(s) are surrounded by a commonsleeve 176 which extends between the housing 124 and the porous mediumhead. The electric wire sleeve 176 has a proximal end 172 close to thehousing 124 and a distal end 174 with the electric connector 160 mountedthereto for connection to the head (not shown). The electric wires andthe electric wire sleeve 176, if any, can extend along the gas exchangetubing 132.

In the embodiment shown, the electric wire sleeve 176 and the gasexchange tubing 132 are flexible components. In some implementations,the electric wire sleeve 176 and/or the gas exchange tubing 132 can berigid components.

The porous medium sensor 120 further includes a protection sleeve 144surrounding at least a section of the gas exchange tubing 132. In theembodiment shown, the protection sleeve 144 also surrounds the electricwire sleeve 176 surrounding the electric wire(s). The protection sleeve144 is a tubular member with a peripheral wall 146 that defines aninternal gas channel 148. At least a section of the gas exchange tubing132 extends in the internal gas channel 148. The protection sleeve 144has a proximal end 150, close to the housing 124 (shown in FIGS. 4 and5), and an opposed distal end, close to the distal end 140 of the gasexchange tubing 132 (shown in FIGS. 2 and 3).

The protection sleeve 144 is a flexible and elongated tubing made of gaspermeable material. Furthermore, in some implementations, the protectionsleeve 144 is rodent resistant (or anti-rodent). In an embodiment, theprotection sleeve 144 includes a metal wire mesh component such as awoven metallic component to offer a protection against rodent damage.

In some implementations, the protection sleeve 144 covers the section ofthe gas exchange tubing 132 including the water-repellent membrane 142.In other implementations, the protection sleeve 144 does not cover thesection of the gas exchange tubing 132 including the water-repellentmembrane 142, the latter being covered solely by an end collar, asdescribed in more details below.

In some implementations, the protection sleeve 144 is made of wovenmaterial like fiberglass, metals, plastics or natural fiber clothing ornon woven geotextile, fiberglass or metals.

Referring back to FIG. 1, there is shown that the porous medium sensor120 further includes a proximal end collar 154 and a distal end collar156. Referring now to FIGS. 4 and 5, there is shown that the proximalend collar 154 has a first end sealed to the gas exchange tubing 132 andthe electric wire sleeve 176, and a second end sealed to the protectionsleeve 144. In some implementations, the first end of the proximal endcollar 154 can be sealed to the housing 124.

If the protection sleeve 144 directly surrounds the electric wire(s),the first end of the proximal end collar 154 can be sealed to theelectric wire(s) and the gas exchange tubing 132.

Referring now to FIGS. 2 and 3, there is shown that the distal endcollar 156 has a first end sealed to the protection sleeve 144 and asecond end. The second end can be a closed end, if the protection sleeve144 does not surround the electric wire(s) or the electric wire sleeve176. In an alternative embodiment, the second end can be sealed to theelectric wire(s) or the electric wire sleeve 176, if any. In theembodiment shown, the second end of the distal end collar 156 is sealedto the electric wire sleeve 176, which extends past the distal endcollar 156.

In the embodiment shown in the figures, the electric wires are assembledtogether and surrounded by the electric wire sleeve 176. The protectionsleeve 144 surrounds the gas exchange tubing 132 and the electric wiresleeve 176. The proximal end collar 154 surrounds the assembly includingthe gas exchange tubing 132, the electric wire sleeve 176, and theprotection sleeve 144. The first end of the proximal end collar 154 issealed to the gas exchange tubing 132 and the electric wire sleeve 176as there is a spacing between the protection sleeve 144 and the housing124. The second end of the proximal end collar 154 is sealed to theprotection sleeve 144. The distal end collar 156 surrounds the assemblyincluding the gas exchange tubing 132, the electric wire sleeve 176, andthe protection sleeve 144 with its first end sealed to the protectionsleeve 144. The second end is sealed to the electric wire sleeve 176,which extends outwardly past the distal end collar 156. The gas exchangetubing 132 and the protection sleeve 144 have their distal ends 140, 152located inside the distal end collar 156. The water-repellent membrane142 is also covered by the distal end collar 156.

The distal end collar 156 covers a free end of the protective sleeve144, a free end of the gas exchange tubing 132, and the water-repellentmembrane 142.

The proximal end collar 154 and the distal end collar 156 are made of awater impermeable material and, in an embodiment, a gas barriermaterial. For instance, the collars 154, 156 can be made of a thermoshrinkable polymer such as and without being limitative any rigid orflexible water impermeable material like rubber, water impermeableplastics, nylon or metals.

Referring to FIG. 3, there is shown that the internal channel 148 of theprotection sleeve 144 has a diameter larger than the combined outerdiameter of the electric wire sleeve 176 and the gas exchange tubing132. Thereby, a gas channel extends longitudinally therein through whichair and other gases can circulate. The gas channel allows air to reachthe water-repellent membrane 142 housed in the gas exchange tubing 132.In an alternative implementation (not shown), the apparatus can be freeof gas channel since the protection sleeve 144 is air permeable.

The distal end of the apparatus further includes a gas chamber 158defined above the water-repellent membrane 142. The gas chamber 158allows gas exchange between atmosphere and the gas exchange channel 136through the protection sleeve 144 and the water-repellent membrane 142.The gas chamber 158 is defined inside the distal end collar 156, i.e.the distal end collar 156 is not sealed to the water-repellent membrane142. Thus, gas exchange between atmosphere and the gas exchange channel136 occurs through the protection sleeve 144, the gas channel, if any,the gas chamber 158, and the water-repellent membrane 142.

In an embodiment (not shown), the protection sleeve 144 can extend pastthe water-repellent membrane 142 and define the gas chamber 158 in thesection of the internal gas channel 148 extending past thewater-repellent membrane 142. In other words, the section of theprotection sleeve 144 which extends past the water-repellent membraneprevents the distal end collar 156 from abutting the water-repellentmembrane 142 and thereby prevents gas exchange.

When the sensing portion 121 of the porous medium sensor 120 is at leastpartially inserted in the porous medium, a section of the assemblyincluding the gas exchange tubing 132, the electric wire sleeve 176, andthe protection sleeve 144 is located outwardly of the porous medium.This section further includes the distal end collar 156. Gas exchangebetween the housing 124 and atmosphere occurs through the protectionsleeve 144, which is gas permeable, the internal gas channel 148extending in the protection sleeve 144, the gas exchange channel 136including the water-repellent membrane 142, and the gas exchangeaperture of the housing 124.

Liquid infiltration in the gas exchange aperture of the housing 124 isprevented through both the distal end collar 156 and the water-repellentmembrane 142. The distal end collar 156 prevents important waterquantity and particles to reach the water-repellent membrane 142.

In the embodiment shown, the protection sleeve 144 extends alongsubstantially the length of the gas exchange tubing 132. However, insome implementations, the protection sleeve 144 can extend along ashorter section thereof. In the embodiment shown, the distal end of theassembly, including the distal end collar 156 covering thewater-repellent membrane 142, prevents partial or complete obstructionof the gas exchange aperture or a portion of the housing 124 which couldbias the pressure or other porous medium property measurements.

To measure a porous medium property, such as matrix water potential, ina porous medium, the sensing portion 121 is first inserted in the porousmedium. The assembly including the gas exchange tubing 132, the electricwire sleeve 176, the protection sleeve 144, and the distal end collar156 extends upwardly with their distal ends extending outwardly of theporous medium.

Once the sensing portion 121 is connected to a power supply (not shown),if needed, the porous medium sensor 120 monitors the porous mediumproperty in the porous medium where the sensing portion 121 is inserted.Gas exchange with the housing 124 inserted in the porous medium andatmospheric pressure therein is ensured through the gas permeableprotection sleeve 144, the gas exchange channel 136 having thewater-repellent membrane 142 inserted therein, and the gas exchangeaperture. Therefore, for pressure measurement purposes, it is assumedthat gas pressure within the porous medium, at the sensing portioninsertion depth, is substantially similar to atmospheric pressure. Themonitored data are transferred to an electronic circuit board which candisplay, transmit and/or record the data.

Liquid and porous material infiltration is prevented by the combinationof the water-repellent membrane 142 and the distal end collar 156, evenif the gas exchange aperture is located in the porous medium. Moreparticularly, the distal end collar 156 limits high pressure water andsmall particles to reach the water-repellent membrane 142. Then, thewater-repellent membrane 142 prevents accidental liquid and porousmedium infiltration which could have entered in the internal spacedefined by the distal end collar 156 and the protection sleeve 144 inthe gas exchange channel 136 and the gas exchange aperture, and therebyprevents partial or complete obstruction of the gas exchange aperturewhich could bias the porous medium property measurements. Whilepreventing accidental liquid and porous medium infiltration, thewater-repellent membrane 142 allows gas communication therethrough.

In the embodiment shown and described above, the assembly including thegas exchange tubing 132, the electric wire sleeve 176, and theprotection sleeve 144 is flexible. In some implementations, at least oneof the gas exchange tubing 132, the electric wire sleeve 176, and theprotection sleeve 144 can be a rigid component and the resultingassembly can be rigid or substantially rigid.

In the implementation shown in FIGS. 1 to 5, the porous medium sensor120 is a tensiometer and the gas exchange aperture is in fluidcommunication with a reference port of the pressure sensor mounted inthe housing 124. It is appreciated that even if the above describedembodiment relates to tensiometers, the assembly including the gasexchange tubing, the water-repellent membrane, the protective sleeve,and the end collar can be mounted to various types of sensing portionssuch as and without being limitable pH, salinity, temperature, humidity,liquid, gas, or gas concentration sensing portions wherein gascommunication between two sections or between a section and atmosphereis wanted while, simultaneously, preventing liquid and porous mediuminfiltration. The sensing portion can also include a sensor detectingthe irrigation status. The sensing portion can also include a LED photodetector for detecting fluid in soils or porous media.

The assembly including the gas exchange tubing, the water-repellentmembrane, the protective sleeve, and the end collar can be used withmodular or single piece sensor apparatuses and with self-priming orfilled fluid chamber sensor apparatuses, and any combination thereof. Itis appreciated that the water-repellent membrane can be replaced by anyliquid repellent membrane which is designed to prevent liquid and porousmedium infiltration in the gas exchange channel.

Moreover, although the embodiments of the porous medium sensor andcorresponding parts thereof consist of certain geometricalconfigurations as explained and illustrated herein, not all of thesecomponents and geometries are essential to the invention and thus shouldnot be taken in their restrictive sense. It is to be understood, as alsoapparent to a person skilled in the art, that other suitable componentsand cooperation therein between, as well as other suitable geometricalconfigurations, may be used for the porous medium sensor according tothe present invention, as will be briefly explained herein and as can beeasily inferred therefrom by a person skilled in the art. Moreover, itwill be appreciated that positional descriptions such as “above”,“below”, “left”, “right” and the like should, unless otherwiseindicated, be taken in the context of the figures and should not beconsidered limiting.

Several alternative embodiments and examples have been described andillustrated herein. The embodiments of the invention described above areintended to be exemplary only. A person of ordinary skill in the artwould appreciate the features of the individual embodiments, and thepossible combinations and variations of the components. A person ofordinary skill in the art would further appreciate that any of theembodiments could be provided in any combination with the otherembodiments disclosed herein. It is understood that the invention may beembodied in other specific forms without departing from the spirit orcentral characteristics thereof. The present examples and embodiments,therefore, are to be considered in all respects as illustrative and notrestrictive, and the invention is not to be limited to the details givenherein. Accordingly, while the specific embodiments have beenillustrated and described, numerous modifications come to mind withoutsignificantly departing from the spirit of the invention. The scope ofthe invention is therefore intended to be limited solely by the scope ofthe appended claims.

The invention claimed is as follows:
 1. A porous medium sensorcomprising: a sensing portion at least partially insertable in a porousmedium and having a housing with a gas exchange aperture defined thereinand a parameter sensor mounted in the housing for measuring a parameterof the porous medium in which the sensing portion is insertable; a gasexchange tubing in gas communication with the gas exchange aperture ofthe sensor portion and having a water-repellent membrane insertedtherein, the water-repellent membrane preventing water infiltration inthe housing through the gas exchange aperture; a gas permeableprotection sleeve covering at least a section of the gas exchangetubing; and a water impermeable distal end collar covering a distal endof the gas permeable protective sleeve and the water-repellent membrane.2. The porous medium sensor as claimed in claim 1, wherein the gaspermeable protection sleeve covers the gas exchange tubing proximate tothe water-repellent membrane.
 3. The porous medium sensor as claimed inclaim 1, wherein a gas chamber is defined between the water-repellentmembrane and the water impermeable distal end collar, the gas chamberbeing in gas communication with the gas permeable protection sleeve. 4.The porous medium sensor as claimed in claim 3, wherein a gas channel isdefined between the gas permeable protection sleeve and the gas exchangetubing and the gas channel being in gas communication with the gaschamber and the water-repellent membrane.
 5. The porous medium sensor asclaimed in claim 1, wherein the water-repellent membrane is inserted inan open-ended gas exchange channel extending through the gas exchangetubing, wherein a first open and proximal end of the gas exchangechannel is aligned with the gas exchange aperture and a proximal end ofthe gas exchange tubing is sealed to the housing, and wherein thewater-repellent membrane is inserted in the gas exchange channel closeto a distal end of the gas exchange tubing.
 6. The porous medium sensoras claimed in claim 1, wherein the gas permeable protection sleevecomprises a peripheral wall including a metal wire mesh component. 7.The porous medium sensor as claimed in claim 1, further comprising aproximal end collar covering a proximal end of the gas permeableprotection sleeve and at least a section of the gas exchange tubing. 8.The porous medium sensor as claimed in claim 1, wherein the waterimpermeable distal end collar is a polymeric heat-shrinkable collar. 9.The porous medium sensor as claimed in claim 1, further comprising atleast one electric wire extending outwardly from the housing and havingat least a section thereof covered by the gas permeable protectionsleeve.
 10. The porous medium sensor as claimed in claim 9, wherein theat least one electric wire extends through and past the waterimpermeable distal end collar.
 11. The porous medium sensor as claimedin claim 1, wherein the water-repellent membrane is porous and gaspermeable and the gas exchange tubing comprises a polymeric water andgas impermeable peripheral wall.
 12. The porous medium sensor as claimedin claim 1, wherein the parameter sensor is selected from the groupcomprising: an electrical transducer, a pressure sensor, a H+-selectivetransducer, an ion-selective transducer, a temperature sensor, ahumidity sensor, a liquid sensor, and a gas sensor.
 13. The porousmedium sensor as claimed in claim 1, wherein the gas exchange tubing isflexible and orientable to extend above the housing and allowing gasexchange between atmosphere and the gas exchange aperture.
 14. A porousmedium sensor comprising: a sensing portion at least partiallyinsertable in a porous medium and having a housing with a gas exchangeaperture defined therein and a parameter sensor mounted in the housingfor measuring a parameter of the porous medium in which the sensingportion is insertable; a gas exchange tubing having a gas and waterimpermeable wall defining a gas exchange channel in gas communicationwith the gas exchange aperture of the sensing portion and awater-repellent membrane inserted in the gas exchange channel, thewater-repellent membrane preventing water infiltration in the gasexchange channel through a distal open end of the gas exchange tubing; agas permeable sleeve covering at least partially the gas exchange tubingand allowing gas communication with the water-repellent membrane; and awater impermeable distal end collar covering at least a section of thegas permeable sleeve and a section of the gas exchange tubing includingthe water-repellent membrane to prevent water infiltration therein. 15.The porous medium sensor as claimed in claim 14, wherein thewater-repellent membrane is inserted in the gas exchange channel closeto the distal open end of the gas exchange tubing and the gas permeablesleeve covers the water-repellent membrane.
 16. The porous medium sensoras claimed in claim 14, wherein a gas chamber is defined between thewater-repellent membrane and the water impermeable distal end collar,the gas chamber being in gas communication with the gas permeable sleeveand wherein a gas channel is defined between the gas permeable sleeveand the gas exchange tubing and the gas channel being in gascommunication with the water-repellent membrane through the gas chamber.17. The porous medium sensor as claimed in claim 14, wherein a proximalopen end of the gas exchange channel is aligned with the gas exchangeaperture and a proximal end of the gas exchange tubing is sealed to thehousing.
 18. The porous medium sensor as claimed in claim 14, whereinthe gas permeable sleeve comprises a peripheral wall including a metalwire mesh component.
 19. The porous medium sensor as claimed in claim14, further comprising at least one electric wire extending outwardlyfrom the housing and having at least a section thereof covered by thegas permeable sleeve and wherein the at least one electric wire extendspast the water impermeable distal end collar.
 20. The porous mediumsensor as claimed in claim 14, wherein the parameter sensor is selectedfrom the group comprising: an electrical transducer, a pressure sensor,a H+-selective transducer, an ion-selective transducer, a temperaturesensor, a humidity sensor, a liquid sensor, and a gas sensor.